How To

How to Change Prop on Mercury Outboard?

The propeller is the main component on the bottom of the outboard motor that drives and turns the boat. Composed of sloping blades that push or pull water away from the boat, props sometimes sustain damage when they hit underwater debris such as logs and submerged limbs. Corrosion can lead to bending, cracking, deformation and even rupture of the propeller. Replacing the propeller takes about 30 minutes to an hour, depending on how hard the propeller is removing from the tree. You can have a look at our cheap outboard motors buying guide to choose the best one for your boat.


  • Place the outboard motor on a dry, level surface. Rotate the engine so that the propeller is facing up.
  • Look inside the center of the prop blade and locate the nut, mounting pin and flat washer that secure the propeller to the propeller shaft. Straighten the pin with the pliers, then pull the pin on the shaft. Place the pin in a safe area.
  • Loosen and remove the propeller shaft mounting nut by turning it counterclockwise with a ratchet, extension and plug. Once the nut is loosened by hand, finish unscrewing the nut with your fingers. Place the nut with the pin. Remove the flat washer that is positioned behind the mounting nut. Place the flat washer with the pin and the fixing nut. you can read our how to mount a transducer on an aluminum boat article.
  • Take the propeller blades and pull the prop up until it slides off the prop shaft. If the propeller is hard to pull, use the rubber mallet to tap the back of the propeller until it is loose enough to remove from the shaft. Finish by pulling the propeller out of the shaft and placing it with the other prop props.
  • Remove any rope, string, fishing line or weeds from the rear of the propeller shaft with a sharp knife before installing the new prop.
  • Match the splines inside the new propeller with the splines on the propeller shaft. Push the stand ultimately onto the shaft until it sits against the thrust washer behind the propeller. Press the new prop gently with the rubber mallet, if necessary, to finally get against the thrust washer.
  • Push the flat washer onto the shaft and against the new prop. The original prop kit should come with new prop accessories. Thread the nut onto the shaft and tighten the nut down with the ratchet, extension and socket until the nut is fully tightened. Turn the kickstand to ensure that it moves freely without any restrictions.
  • Insert the new pin into the shaft in front of the mounting nut. Fold the pin with the pliers to prevent it from vibrating on the shaft. The original prop is now ready for the water.

Tips and Warnings

  • Some driveshafts have a square shaft that sits inside a recessed groove on the side of the propeller shaft. The shaft-side spindle slides into the recess in the center of the new prop blade. This type of propeller shaft is designed for the square shaft on the propeller shaft to turn the prop blade.
  • If the attachment is stuck and does not come off the propeller shaft, you will need a prop extractor to remove it.
  •  Wear protective gloves when using a sharp knife to cut any old ropes, chains or weeds at the rear of the propeller shaft.

Leave a Comment

Your email address will not be published. Required fields are marked *


This site uses Akismet to reduce spam. Learn how your comment data is processed.